OFFSET
3,1
COMMENTS
a(17) <= 1340770739, a(18) = 144729585, a(19) <= 9381302307, a(20) <= 1257818848, a(21) <= 6299438145, a(22) <= 32911706919, a(23) <= 26720105555, a(24) <= 3141537984, a(25) <= 59558175105, a(26) <= 71119743695, a(27) <= 260207700831, a(28) <= 28582652736, a(29) <= 688883385190, a(30) <= 593086020813. - Chai Wah Wu, Oct 14 2020
LINKS
Martin Ehrenstein, Table of n, a(n) for n = 3..40
Eric Weisstein's World of Mathematics, Polygonal Number
EXAMPLE
a(3) = 9 because 9 = 10 - 1 = 15 - 6 = 45 - 36 and this is the least integer that can be expressed as the difference of two triangular numbers in exactly 3 ways.
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Oct 10 2020
EXTENSIONS
a(11)-a(16) from Chai Wah Wu, Oct 13 2020
a(17) and a(19)-a(40) from Martin Ehrenstein, Oct 23 2020
STATUS
approved